For industrial robots, especially the ones designed to work in limited and complex workspaces, flexibility and compactness are among the major design requirements, and routing plays a more and more important role in the applications of robots.
A robot typically comprises one or more rotary joints in order to achieve flexible positioning of robot arms. Generally, the larger the rotation ranges of rotary joints are, the more flexible a robot is. However, in order to transmit fluid, power and various signals to and from robot arms, one or more air hoses or cables typically go through each rotary joint, and thus it is important to route both the cables and hoses. These hoses or cables cannot bear too much bending and twisting for a long time, which has become one of the major difficulties for large rotation ranges of rotary joints.
Various attempts have been made to solve the problem of routing in limited spaces, for example, cables and hoses go through the tube shaft in the middle, and the drive unit, e.g. motors and gear box sets, are arranged nearby. A variant of tube shafts is the hollow gear boxes. However, one disadvantage of this kind of structure is that the connection between the tube shaft and motor requires the usage of gear box sets or belts. This will introduce additional steps for backlash adjustment, and more risk of component failure. And non-coincident placement of joint axis and drive units require makes the compact design of robot arms more difficult.
One improved design to avoid the disadvantages mentioned above is to use special kinds of drive units, e.g. a drive unit including hollow motors and reducers, and with hollow shafts, as shown in FIG. 1A. This kind of component simplifies the structure of joints significantly, and makes the routing more easily. But the cost will be much higher than the common ones.
Another solution is using new materials, such as FPC. Less space needed and longer lifetime makes FPC a preferable routing solution, as shown in FIG. 1B. However, the usage of this design could be limited because it doesn't provide routing solutions for air hoses.
Another developed solution is combining hollow gear box structure and FPC solution. As shown in FIG. 1C, this solution uses FPC to transfer power and signal instead of conventional cables, while let air hose go through the hole of the hollow gear box. It reduces the parts needed to go through the hollow gear box, and use the advantages of FPC, which could help to make the joint compact, cost competitive and flexible. However, it needs a hollow gear and also has the problem of the non-coincident for the axis of the motor and the gear.
In view of the foregoing, there is a need in the art to develop an improved routing structure to route both the cables and hoses, and an improved rotary joint.